1. Field of the Invention
This invention relates to the field of liquid treatment and purification and, in particular, to a method of treating a liquid with a ringing magnetic flux whereby an oxidizing agent having prolonged effectiveness is formed and stabilized in the liquid. The method of the present invention may be used for the treatment of any liquid where biocidal and or biostatic activity is needed and is particularly suited to the treatment of water containing undesired bacteria and/or other microorganisms.
2. Description of Related Art
Various attempts and investigations have been made in the past in respect to the possible use of static and/or time varying magnetic field for the purpose of reducing or eliminating undesirable effects of microbes in various solids and liquids. For example, a summary of various known methods using static and/or time varying magnetic fields for the treatment of food products is given in an article entitled xe2x80x9cKinetics of Microbial Inactivation for Alternative Food Processing Technologiesxe2x80x94Oscillating Magnetic Fieldsxe2x80x9d, issued by the U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, under date of Jun. 2, 2000. In the various methods described by this article the general effect of the magnetic fields is taken to be that of having some sort of mechanical effect on the target microorganisms, such as mechanical disruption of cell structure so as to either kill cells or to impair their vitality and reproductive capacity.
In the past, Clearwater Systems, LLC, the assignee of this application, has manufactured and sold a device for use in magnetically treating liquids, which device is the subject of U.S. Pat. No. 6,063,267 and is sold under the trademark xe2x80x9cDolphinxe2x80x9d. As originally conceived, the Dolphin device was seen to be one primarily for use in treating water to prevent the depositing of scale onto the walls of pipes, tanks and other equipment handling water in both domestic and industrial situations, instead causing the minerals to form power in the bulk solution, and it was also seen to have an antimicrobial effect by way of causing microorganisms to become encapsulated in shells of the mineral powder formed in lieu of the mineral scale.
In more detail, the past known effect of the Dolphin device for the control of microorganisms in water was related to the Dolphin device causing the precipitation of calcium carbonate and other dissolved minerals in the water to form crystals or proto-crystals of calcite/aragonite and vaterite or the like. As these crystals or proto-crystals grow and aggregate with one another, under the influence of the oscillating magnetic flux produced by the Dolphin device, they also combine, primarily non-chemically, with the microorganisms in the water, thereby encapsulating the microorganisms with the material of the crystals or proto-crystals and in this way kill the microorganisms or at least inhibit their reproduction and growth.
As the result of recent work and further investigation in respect to the Dolphin device, Applicants have discovered that, under certain conditions, the treatment of liquids by ringing magnetic flux of the type produced by the Dolphin device has a further previously unrecognized and unanticipated effect on controlling microbial activity in the treated liquid. That is, Applicants have discovered that the bursts of ringing magnetic flux created by the Dolphin device not only are beneficial in reducing or eliminating scale deposits and encapsulating microbes in precipitated mineral material, but also, under certain conditions of operation, can produce a stabilized oxidizing agent in the water, which oxidizing agent then chemically reacts with microorganisms by oxidizing components of the cell structure to either quickly kill the microorganisms or to at least creating sub-lethal injury that reduces microorganism population. The exact nature of the oxidizing agent is not yet known in full detail, but Applicants strongly believe it to be a stabilized form of hydrogen peroxide, as explained in more detail hereinafter.
Hydrogen peroxide is a known oxidizing agent which has favorable anti-microbial activity with decomposition products comprising water and oxygen (i.e., harmless byproducts) making it ideal for water treatment or water purification systems. However, the previous use of hydrogen peroxide and other oxidizing agents in water treatment systems has been costly and troublesome since the oxidizing agent is generally added to the water in question as a separate purchased product. This aspect makes these prior art water treatment systems expensive and difficult. Further, when pure hydrogen peroxide is added in batch doses to water or other liquid it quickly decomposes before it can effectively oxidize microorganisms, and it does not become uniformly or homogeneously distributed throughout the concerned body of liquid. Thus, it would be beneficial to provide a way much simpler, less costly, and better able to obtain a uniform distribution of hydrogen peroxide for treating water with hydrogen peroxide or similar oxidizing agent.
The use of hydrogen peroxide to treat biofilms also has great utility in water treatment systems. Biofilms of bacteria can reside and colonize in pipes, and are particularly prevalent and of concern in the open-loop water circuit of air conditioning system cooling towers. They have been heretofore difficult to eradicate given the complex matrix in which the bacteria reside such that anti-microbial agents have difficulty penetrating the matrix. Some known water treatment systems concentrate on scale removal and encapsulation of bacteria in the water. However, given the biofilm matrix, encapsulation of the individual bacteria is nearly impossible. Thus, it would be advantageous to provide a water treatment system which can treat and prevent biofilms utilizing a stabilized form of hydrogen peroxide or other oxygen-rich oxidizing agents. By xe2x80x9cstabilizedxe2x80x9d it is meant that the hydrogen peroxide or other oxidizing agent is not in an unstable pure form but instead is in a more stable form, in which it has complexed with compounds or ions inherent in the water, allowing its concentration to be gradually increased as the water or other liquid is recirculated past a treatment zone with the concentration becoming uniform throughout the whole body of treated liquid.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a simple method and means of generating stabilized hydrogen peroxide or other oxygen-rich oxidizing agent for liquid treatment and purification.
It is another object of the present invention to provide a method of generating stabilized hydrogen peroxide or other oxygen-rich agent to destroy and/or inhibit the growth of biofilms in water and other liquids.
Still other objects and advantages of the invention will be apparent from the following specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a method of generating an oxidizing agent in a treated water based liquid, the method comprising the steps of: providing a magnetic field in the form of successive bursts of ringing magnetic flux; exposing a liquid to the magnetic field for a period sufficient to form an oxidizing agent in the liquid; and maintaining a pH of between 7 to 10, preferably 8 to 9, in the liquid to stabilize the oxidizing agent. Preferably, in the step of exposing a liquid to the flux, the liquid comprises water and the oxidizing agent formed comprises hydrogen peroxide. For convenience, hereinafter the treated liquid will be taken to be water, and the produced oxidizing agent will be taken to be hydrogen peroxide, but the invention, at least in its broader aspects, is not limited to water and hydrogen peroxide.
The method further includes the step of continuing to expose the water to the magnetic flux, preferably by continuously recirculating portions of the water body through the treatment zone, so that the stabilized hydrogen peroxide agent accumulates uniformly in the water. It is also required that a significant amount of dissolved oxygen be in the water which passes through the treatment zone, and preferably this is achieved by aerating the water after it is taken from the main body of water, for recirculation purposes, and either before or after passing through the magnetic field treatment zone. Where the water application is that of use in a cooling tower the aeration may, and preferably does, occur during normal operation of the cooling tower when recirculated water passes over the evaporative surfaces of the cooling tower in the presence of ambient air. The ringing magnetic flux occurs in successive periods with flux oscillations during a ringing period being of a primary frequency between 10 kHz and 80 kHz, plus harmonics, and with the ringing period being repeated at a frequency of between 1 Hz to 100 Hz, and preferably of between 50 Hz to 60 Hz.
In another aspect, the present invention is directed to a method of forming an oxidizing agent in water comprising the steps of: aerating the water; providing a means in close proximity to the water for inducing bursts of ringing magnetic flux in the water having a frequency of 10 kHz to 80 kHz during each burst wherein the bursts are repeated at a frequency of 1 Hz to 100 Hz, preferably 50 Hz to 60 Hz, exposing the water to the bursts of ringing magnetic flux for a time sufficient to form a significant amount of oxidizing agent in the water; and maintaining the water body at a pH of about 7 to 10, preferably 8 to 9, to stabilize the oxidizing agent.
In yet another aspect, the present invention is directed to a method of making hydrogen peroxide or a complex thereof in water, the method comprising the steps of: providing a water source; providing a ringing magnetic flux in close proximity to the water source; exposing the water source to the ringing magnetic flux for a sufficient number of repetitive passes through the ringing flux to form stabilized hydrogen peroxide or a complex thereof in the water; and maintaining a pH of about 7 to 10, preferably 8 to 9, to stabilize the hydrogen peroxide or complex thereof. The water source may be that of a cooling tower. In the step of providing a ringing magnetic flux, the ringing magnetic flux has a frequency of 10 kHz to 80 kHz, plus harmonics, during each ringing period, and the ringing periods repeat at a frequency of 1 Hz to 100 Hz, preferably 50 Hz to 60 Hz. The means for producing the ringing magnetic flux may comprise an inductor or set of inductors in close proximity to the water; a power supply source electrically connected to the inductor or set of inductors having a frequency of 10 kHz to 80 kHz; and a switch in series with the inductor or set of inductors and the power supply source, with an associated controller for the switch alternately opening and closing the switch at a rate of 1 Hz to 100 Hz, preferably 50 Hz to 60 Hz, to provide a succession of ringing periods of magnetic flux passing through the water.
In still another aspect, the present invention is applied to specifically treating water in an air conditioning system cooling tower having an inlet and outlet for water to recirculate water from a maintained body of water through the cooling tower. In this case, the recirculated water is exposed, at a treatment zone, to the bursts of ringing magnetic flux during its recirculation, either before or after its flowing through the water evaporation portion of the cooling tower, to maintain a significant level of dissolved oxygen in the water.
In all embodiments of the inventive method the step of forming an oxidizing agent in the treated water is one wherein the hydrogen peroxide or other oxidizing agent generated is of a stabilized form which does not quickly lose its biocidal and/or biostatic properties and which therefore increases in concentration, homogeneously throughout the body of water, to a desired level as portions of the water body are re-circulated through the magnetic flux treatment zone.